Insulator shield



NOV. 16, 1937. D, SMITH 2,099,540

INSULATOR SHIELD Filed May 10, 1934 INVENTOR D. H. SMITH Patented Nov.16, 1937 UNITED STATES PATENT OFFICE INSULATOR SHIELD Application May10, 1934, Serial No. 724,972

8 Claims.

This invention relates to insulator shields or guards and particularlyto guards designed primarily to protect insulators or portions thereoffrom being broken by stones, missiles, or the like,

directed at the insulator.

The principal object of this invention is to provide a shield which willeffectively dissipate or absorb the shock of impact of missiles or thelike in such a manner as to avoid the transmittal of any considerableportion of the shock to the insulator directly.

In certain areas or localities where telegraph, telephone or similarlines of wires are supported in the open upon poles in the well knownmanner, considerable difficulty has been experienced in having theinsulators broken'by stones or the like, thrown by persons indulging inmalicious mischief. In certain particular localities where the restraintupon such persons is extremely lax the item of replacing insulatorsperiodically has become not only one of particular annoyance but alsoone of considerable expense. Therefore, it is highly desirable in somelocalities to employ some type of protecting means for the insulators.Investigation of devices which have been designed for the protection ofinsulators has indicated that such devices have not, in general, beenpractical for use on telegraph, telephone, or similar lines. Among theobjections which have been found in such devices are: (1) their cost,(2) the fact that they are not particularly effective, and (3) theiradverse effect upon the insulating qualities of the insulator.

Having made this finding a new type of insu- 35 lator shield was devisedaccording to this invention which not only affords satisfactoryprotection for insulators but which may be inexpensively manufacturedand readily installed upon insulators either before or after theinsulators 40 are in place.

Another object of this invention is to provide a shield of the typedescribed herein which is attached loosely to the insulator instead ofbeing aflixed relatively rigidly thereto, so that a minimum amount ofthe shock or impact upon the shield will be transmitted through itsmounting to the insulator body.

Another object is to provide an insulator shield which will turn uponits mounting so that the 50 inertia of the shield itself may beeffective in partially absorbing the shock or impact of glancing blows.

A further object is to provide corrugations in the body of the shield sothat a missile on impacting the shield will in a majority of casesstrike upon the corrugated portions which are held out of direct contactwith the insulator body and whereby the yielding or distorting of thecorrugations will provide a cushioning effect to the impact. 5

These and other objects will be apparent from the following descriptionand claims taken in connection with the accompanying drawing forming apart of this application, in which- Fig. 1 is an assembled view partlyin section, 10 and Fig. 2 is a sectional view on the line 22 of Fig. 1.

As shown in the drawing the insulator and shield combination embodies aninsulator I0, 15 shown as the ordinary double petticoat type ofinsulator used largely in the telegraph art. The insulator embodies ahead portion l I and a lower petticoat portion [2. Between the head andthe petticoat is a wire groove I3 formed between upper and lower lips.Preferably the petticoat portion of the insulator flares outwardly fromthe root of the lower lip of the groove [3. The outer surface of thepetticoat may be either frustoconical or spheroidical in outline.However, the application of the shield is not limited to this type ofinsulator. It may be applied to any other types of petticoat insulatorswhich are supported on pins for the purpose of carrying telegraph,telephone, or other types of wires. Where, however, an insulator has astraight cylindrical petticoat, the shield can only be applied if theinsulator has a supporting shoulder or head to engage the upper portionof the shield.

Referring to Fig. 1 the insulator Ill has a shield !4 made of twoidentical halves I5 and 16. These halves are held together by a tongueI! provided at one side of each half to pass through the slot of an ear[8 disposed at the other side to cooperate with the tongue. The generalshape of each half is that of a truncated or frustated cone dividedalong its vertical axis. The outline of the half of the shield is moreclearly illustrated in Fig. 2. The shield being made in two parts can beplaced around the petticoat of the insulator even though the insulatoris in service bearing a telegraph wire or the like upon the cross arm ofa pole. When the two halves are placed around the petticoat of theinsulator and the tongues inserted in the slots, the assembled form ofthe insulator is that of a truncated cone with its upper edge adjacentthe top of the petticoat portion of the insulator and its lower edgejust below the lower edge of the insulator as shown in Fig. 1. i

The shield is designed so as to permit a moderately loose fit whenclamped in place about the upper portion of the petticoat, the fit beingsuch corrugations.

that when the insulator is held rigid, the shield may be readily turned.The advantage of this is that it permits the shield to rotate whenimpacted with a glancing blow. This assists the shield in warding 01 theblow and also in largely preventing the transmission of shock to theinsulator. The conical dimensions or outline of the shield is such thatthe lower portion of the shield flares out away from the petticoatgiving additional protection from a direct impact which might otherwisebe transmitted to the lower or more vulnerable portion of the petticoat.The manner in which this protection is accomplished is due to the factthat while the shield is fitted loosely about the yoke or upper portionof the petticoat. it is preferable that little pivotal or tiltingmovement of the shield be permitted between it and the insulator. Astone or other missile directed at the shield in order to transmit itsshock of impact directly to the petticoat must dent or bend the shieldinward at the point of impact. The distance between the shield and thepetticoat is preferably of'such an amount as to require considerablebending or deformation in order 'to bring the impacted portion incontact with the petticoat. From the fact that the shield stands; offfrom the petticoat with a flaringv or annular separating spacetherebetween, it will be seen that the less rigid portion of the shield,the lower portion, is positioned farthest from the petticoat. On theother hand, the upper stiffer portion of the shield is positionedclosest to the petticoat.

The shield is preferably made of sheet metal embodying corrugationscovering substantially its entire surface. In its preferred form aseries of corrugations are formed in themetal, by suitable stampingprocess or otherwise, running parallel to the base of the shield. It hasbeen found in. tests that corrugations improve the eifectiveness of theshield over that of one not embodying However, it has also been foundthat corrugations are most effective in the form of annular ringssubstantially parallel to the base of the shield. V

corrugations in the form of annular rings are most effective in thatthey provide more rigidity to the lower, unsupported portion of theshield than corrugations of other forms, and that they havea tendency todistribute the effect of the blow over a large area of the insulator.

The number and spacing of the corrugations and the rigidity of the metalis also of importance.

The corrugations should be so closely spaced that the average missile orstone that may impact the shield will strike upon .the outer ridge orbody of the corrugations and thereby be prevented from impacting thegroove portion of the shield which may be brought into immediate contactwith the insulator. It has been found in regard to the rigidity of themetal that if the softness i and the gauge of the metal renders theresistance to impact too-light, the corrugations in the shield yield tooreadily and permit the shock to be transmitted directly to the glass atthe point of impact. On the other hand, when the gauge is too heavy orthe metal too hard the shock is transmitted with vsuiiicient force tocause the insulator to be bro ken at the point which supports theshield. It was found that if the corrugations were of such size or depthand spaced at such J; a distance apart as to add materially to thestiffness of the shield formed from a metal of a suitable thickness andhardness, the shield has a sufficient stiffness to stand up under impactand yet have a suitable resiliency to absorb a sufficiently large partof the impact to prevent the shock from being transmitted to theinsulator with a force great enough to damage the same.

A specific example of a shield meeting the above requirementsv willserveto furtherillustrate the method of construction. It has been foundthat for a shield having the shape of a truncated cone 1% inches highand having radii of 2%; inches and 1 inches respectively at the bottomand top, was required to be made of No. 20 U. S. S.

gauge mild steel or No. 22 U. SE. gauge cold rolled Monel metal. In thisshield the corrugations were formed with inch outside radius spaced inchapart on centers. A shield made according to these specifications provedout repeatedly in tests of several samples to best meet the conditionsset forth above.

Shields constructed in this manner proved in actual tests capable ofwithstanding a blow. sufficient to shatter the wood cob which supportedthe insulator without any damage to the latter. In actual field teststhe shielded insulators were subjected to as many as 40 to; 60 blowswith 2 /2 inch stones thrown by persons from a distance of 5 feetwithout materially damaging theinsulator and without impairing theinsulating di electric strength of the insulator. On the other hand, inthe field test unprotected insulators were shattered upon the firstdirect hit.

Electrical testsmade on shielded and unshielded insulators showed thatthe shielding did not increase the electrical leakage of the insulators.

Inother words, insulators may be protected with shields constructedaccording to this invention without impairment of their insulatingproperties, and without in any way interfering with the method ofinstalling insulators already in practice. A particular advantage of.this type of shield is that it maybe installed upon insulators which arein service without in the least disturbing the insulators or the wire orwithout discontinuing service over the wires while the installation isbeing. made.

Insulator shields which protected the petticoat portion only were found,besides the advantages;

of installation already set forth, to sufficiently protect insulatorsfrom breakage by missiles or stones hurled against them without coveringthe entire insulator. It was found that no protection was needed for theportion of the insulator above the line of the petticoat. thickness, ofthe parts of the insulator above this. point appear to sufficientlywithstand blows to make breakage in this area rather infrequent. It isthere-fore clearly indicated that if the most vulnerable portion of theinsulator was protected, that the insulator as a whole stood up..Fromthe above description it will be seen that a most effective meanshas beendevised for protecting insulators of the pintype havingdepending petticoats. In addition this has been developed in' a formwhich may be inexpensively manufactured and easily assembled.

It should be understood that the particular shape both of the insulatorand the shield shown in the drawing is merely illustrative and that thesame principles may be employed for fitting shields to any type ofinsulator having a vulnerable area which needs protection.

Although this invention has been shownin but. one form it will. beevident tothose skilled in the The shape and i art that many other formsand modifications may be employed without departing from the spirit ofthis invention as described above or as set forth in the appendedclaims.

What is claimed is:

1. In combination with an insulator having a portion thereof subject tobreakage by the force of impact of an object, a shield having asubstantial portion thereof spaced from and extending over saidbreakable portion of the insulator to protect the latter from breakage,said shield being turnably mounted to cause the same to turn by theforce of impact of an object glancing upon the shield whereby the shockof said impact will be partially absorbed by the turning movement of theshield.

2. In combination with an insulator having a petticoat portion, a shieldformed to cover the petticoat portion, and resting upon the insulatoradjacent to the upper portion of the petticoat, said shield hanging freeabout the waist of the petticoat and having an opening therein at theplace where it rests on the insulator, said opening in the shield beingsufiiciently larger than the insulator to cause the shield to rotateunder the force of impact by an object glancing upon the shield wherebythe shock of said impact will be partially absorbed by the rotationalmovement of the shield.

3. In combination with an insulator having a petticoat portion, a shieldhaving a frusto-conical shape and resting near its upper edge directlyupon a shoulder formed on the insulator adjacent the upper portion ofthe petticoat, said shield being arranged to hang loosely and movefreely about said shoulder and stand out from the petticoat to provide afree pivotal movement about the shoulder, whereby the force of impact ofan object upon the shield will be partially absorbed by the inertia ofthe shield to the limited movement.

4. In combination with an insulator, a shield having the conformation ofa truncated cone and arranged to rest adjacent its small end directlyupon the insulator with a loose and unrestrained fit permitting freemovement and to flare out from the insulator remotely from its restingpoint so that the shield will move against the petticoat under impactthereby to distribute the force of the blow through moving contactbetween the insulator and the shield.

5. In combination with an insulator having a petticoat, a shield for thepetticoat having the conformation of a truncated cone and arranged torest adjacent its upper end loosely upon the insulator adjacent thewaistline of the petticoat, said shield being formed to flare out fromthe insulator remotely from said resting point and extend downwardlyover the petticoat, said shield being formed of pliable but relativelyresistant sheet metal and having substantially its entire surfacecorrugated to provide a cushioning effect for absorbing the shock ofimpact of blunt objects directed at the petticoat portion of theinsulator.

6. In combination with an insulator having a petticoat portion thesurface of which is smooth, a shield of corrugated metal supported uponthe insulator and covering the petticoat, said corrugations providing aplurality of lines of contact with the insulator whereby the force ofimpact of an object directed at the shield will be distributed over anextended area of the insulator.

'7. In combination, an insulator embodying an outwardly flaringpetticoat portion and a wire groove disposed above said petticoat, ashield disposed entirely below said wire groove and formed toprotectively encase said petticoat and arranged to be loosely supportedupon the insulator below said wire groove adjacent the upper portion ofsaid petticoat, said shield comprising a skirt member dividedlongitudinally to form two separate elements, said elements havingcooperating tongues and slots at adjoining edges thereof for engagementwith each other.

8. In combination, an insulator embodying an outwardly flaring petticoatportion and a wire groove disposed above said petticoat, a shielddisposed entirely below said wire groove and encasing said petticoat,said shield being arranged to be loosely supported upon the insulatorbelow said wire groove adjacent the upper portion of said petticoat,said shield comprising a skirt member divided longitudinally to form twoseparate engaging elements, said elements having operating tongues andslots disposed at the adjoining edges thereof so as to be engageablewith each other, said tongue and slot arrangement providing the solemeans for restraining the disengagement of said shield elements.

DONALD H. SMITH.

